The present invention relates to an ink jet system printer of the charge amplitude controlling type and, more particularly, to a phase detection system in the ink jet system printer of the charge amplitude controlling type.
In an ink jet system printer of the charge amplitude controlling type, print distortion is mainly caused by interaction of ink droplets and air resistances occurring during travel of the ink droplets from a nozzle to a record receiving member. Accordingly, to minimize the print distortion, it is required to reduce the travel distance of the ink droplets.
A phase sensor electrode is conventionally disposed between a charging electrode and deflection means in order to detect charge conditions of phase detection ink droplets. The detection of the charge conditions of the phase detection ink droplets is necessary to perform accurate printing as disclosed in U.S. Pat. No. 4,025,926 entitled "PHASE SYNCHRONIZATION FOR INK JET SYSTEM PRINTER" on May 24, 1977, and in U.S. Pat. No. 3,769,632 entitled "DIGITAL PHASE CONTROL FOR AN INK JET RECORDING SYSTEM" on Oct. 30, 1973.
To minimize the above-mentioned travel distance of the ink droplets, it is very effective to omit the phase sensor electrode. Accordingly, an object of the present invention is to minimize a travel distance of ink droplets from a nozzle to a record receiving member in an ink jet system printer of the charge amplitude controlling type.
Another object of the present invention is to provide a novel phase detection system which does not require a phase sensor electrode disposed between a charging electrode and deflection means.
Still another object of the present invention is to provide a novel deflection means which can minimize the travel distance of the ink droplets in an ink jet system printer of the charge amplitude controlling type.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a detection circuit is connected to an ink droplet issuance unit for detecting an electric current flowing through the ink droplet issuance unit to ink liquid contained in the ink droplet issuance unit. This is based on the inventors' discovery that the electric current flows through the ink droplet issuance unit to the ink liquid when an ink droplet is properly charged by charging means. An output signal of the detection circuit is used as a phase OK signal for conducting phase synchronization operation.
Deflection means comprises an upper electrode plate and a bottom electrode plate for establishing a high voltage electric field therebetween. The upper electrode plate is connected to a high voltage source, and the bottom electrode plate is grounded. The bottom electrode plate is fixed to a beam gutter for collecting ink droplets not contributing to actual writing operation, thereby minimizing the travel distance of the ink droplets.